Anthony Brown, the FBI informant who reported on abuse within L.A. County jails, is serving 423 years to life for armed robbery and has a history of making unfounded allegations about police.

For months, Anthony Brown fooled his jailers into believing that he was just another prisoner inside Men's Central Jail.

In fact, the 45-year-old armed robber was working for the FBI on a highly sensitive investigation of the Los Angeles County jails. He took down the names of sheriff's deputies who he alleged were dirty. He reported tales of violent abuse of inmates at the hands of jailers. He even ensnared a deputy in a phone smuggling scheme that resulted in a criminal conviction.

Brown gave FBI agents what they couldn't have gotten on their own: an insider's view of a jail system beset with allegations of excessive force and other deputy misconduct.

But the same knack for duplicity that made Brown a successful informant could complicate the larger case federal prosecutors are building on alleged abuses inside the nation's largest jail system.

Until now, little has been known about the informant. But The Times confirmed his identity and spoke to him at length at Centinela state prison in Imperial County, where he's serving 423 years to life for armed robbery.

Interviews and court records reviewed by The Times paint a complex portrait of the inmate who set off the recent upheaval inside the Sheriff's Department — a bank robber and crack cocaine addict who has a history of lying and making dubious allegations against law enforcement.

Brown's credibility speaks to the larger challenges the FBI faces in its investigation of jail abuses. As with any jailhouse probe, inmates inherently play a central role, but few come without baggage.

To prove crimes by deputies, experts say federal authorities will need to substantiate their charges independently — and it appears they're trying.

Federal investigators, who declined to comment for this story, have secured recordings, internal documents and interviews with multiple officials from within the sheriff's own ranks, persuading some to cooperate in their widening probe. It's not clear what role, if any, Brown will play in any future indictments.

Parts of Brown's story were impossible to substantiate and seemed unlikely. Still, some of his allegations can be corroborated.

His claim that he successfully manipulated a jailer to smuggle him a cellphone has already resulted in that deputy pleading guilty to bribery. And a source with knowledge of the FBI's probe confirmed that federal authorities were investigating another of Brown's allegations — that after his cover was blown, sheriff's officials attempted to hide him from his FBI handlers by moving him from jail to jail under multiple aliases.

Court records show Brown, a New Yorker, told police that before he turned to crime he had worked in the entertainment industry, including a stint at Def Jam Recordings operating "right under" co-founder Russell Simmons. (A company representative, however, found no record of Brown as an employee or contractor.) Brown says he came to California in 2004 as a sound engineer for singer Beyonce's nationwide tour. But eventually he began using crack cocaine, traversing Los Angeles by bicycle, high and looking for places to rob.

By 2005, he was charged and convicted in three bank robberies and sent to prison. Though he confessed, he later changed his story, alleging he was innocent and accusing a detective of committing perjury at his trial. His allegations were dismissed.

He was released in 2009. In his interview with The Times, Brown said it was then that he was approached by the FBI and asked to work as an informant, a role he says he had performed for federal authorities decades earlier on an unrelated investigation in New York.

This time, he said, agents wanted him to go behind bars on a phony gun charge and catalog instances of deputy misconduct. He would not elaborate on how the FBI had chosen him.

An FBI spokeswoman declined to comment for this story, and The Times was unable to corroborate exactly how and when he became an informant.Sources familiar with the case as well as the attorney for the deputy who pleaded guilty to bribery this year confirm Brown was the informant.

Brown did end up back behind bars later in 2009, not on the phony charge, but for another series of armed robberies. He detailed the crimes in a recorded interrogation but then denied the crimes in court, accusing a detective of allowing him to smoke crack in return for a false confession.

During his court case, Brown, who is black, also accused his attorney of using a racial slur against him, but he later wrote to a judge admitting the attorney never used the term. Court records show that another judge determined that Brown made other false complaints, ultimately telling him: "I don't believe a word you have to say."

Brown was incarcerated at Men's Central Jail, where he began working for the FBI.

In his interview with The Times, Brown alleges that he delivered notes about corrupt and brutal deputies during weekly visits with his FBI handler.